Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Queen Marchesa

Deathtouch, haste
When Queen Marchesa enters, you become the monarch.
At the beginning of your upkeep, if an opponent is the monarch, create a 1/1 black Assassin creature token with deathtouch and haste.

Shivan Dragon

Flying
{R}: This creature gets +1/+0 until end of turn.

Serra Angel

Flying
Vigilance (Attacking doesn't cause this creature to tap.)